Dowlais was the site of Dowlais Ironworks, founded in 1759 by John Guest and later the largest ironworks in the United Kingdom. Guest's reliance on the exploitative "truck" (company shop) system contributed to the outbreak of the Merthyr Uprising. 

Of the hill "Dowlais Top," the poet Idris Davies (1905-53) wrote: 

I used to go to St John’s Wood
On Saturday evenings in summer
To look on London behind the dusty garden  trees,
And argue pleasantly and bitterly
About Marx and Heine, the iron brain and the laughing sword;
And the ghost of Keats would sit in a corner,
Smiling slowly behind a summer of wine,
Sadly smiling at the fires of the future.
And late in the summer night
I heard the tall Victorian critics snapping
Grim grey fingers at London Transport,
And sober, solemn students of James Joyce,
Dawdling and hissing into Camden Town.
 
But now in the winter dusk
I go to Dowlais Top
And stand by the railway bridge
Which joins the bleak brown hills,
And gaze at the streets of Dowlais
Lop-sided on the steep dark slope,
A battered bucket on a broken hill,
And see the rigid phrases of Marx
Bold and black against the steel-grey west,
Riveted along the sullen skies.

And as for Heine, I look on the rough
Bleak, colourless hills around,
Naked and hard as flint,
Romance in a rough chemise.